srs/trunk/src/kernel/srs_kernel_aac.cpp

/*
The MIT License (MIT)

Copyright (c) 2013-2015 winlin

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
the Software, and to permit persons to whom the Software is furnished to do so,
subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/

#include <srs_kernel_aac.hpp>

// for srs-librtmp, @see https://github.com/winlinvip/simple-rtmp-server/issues/213
#ifndef _WIN32
#include <unistd.h>
#endif

#include <fcntl.h>
#include <sstream>
using namespace std;

#include <srs_kernel_log.hpp>
#include <srs_kernel_error.hpp>
#include <srs_kernel_stream.hpp>
#include <srs_kernel_file.hpp>
#include <srs_kernel_codec.hpp>

#define SRS_FLV_TAG_HEADER_SIZE 11
#define SRS_FLV_PREVIOUS_TAG_SIZE 4

SrsAacEncoder::SrsAacEncoder()
{
    _fs = NULL;
    got_sequence_header = false;
    tag_stream = new SrsStream();
}

SrsAacEncoder::~SrsAacEncoder()
{
    srs_freep(tag_stream);
}

int SrsAacEncoder::initialize(SrsFileWriter* fs)
{
    int ret = ERROR_SUCCESS;
    
    srs_assert(fs);
    
    if (!fs->is_open()) {
        ret = ERROR_KERNEL_AAC_STREAM_CLOSED;
        srs_warn("stream is not open for encoder. ret=%d", ret);
        return ret;
    }
    
    _fs = fs;
    
    return ret;
}

int SrsAacEncoder::write_audio(int64_t timestamp, char* data, int size)
{
    int ret = ERROR_SUCCESS;
    
    srs_assert(data);
    
    timestamp &= 0x7fffffff;
    
    SrsStream* stream = tag_stream;
    if ((ret = stream->initialize(data, size)) != ERROR_SUCCESS) {
        return ret;
    }

    // audio decode
    if (!stream->require(1)) {
        ret = ERROR_AAC_DECODE_ERROR;
        srs_error("aac decode audio sound_format failed. ret=%d", ret);
        return ret;
    }
    
    // @see: E.4.2 Audio Tags, video_file_format_spec_v10_1.pdf, page 76
    int8_t sound_format = stream->read_1bytes();
    
    // @see: SrsAvcAacCodec::audio_aac_demux
    //int8_t sound_type = sound_format & 0x01;
    //int8_t sound_size = (sound_format >> 1) & 0x01;
    //int8_t sound_rate = (sound_format >> 2) & 0x03;
    sound_format = (sound_format >> 4) & 0x0f;
    
    if ((SrsCodecAudio)sound_format != SrsCodecAudioAAC) {
        ret = ERROR_AAC_DECODE_ERROR;
        srs_error("aac required, format=%d. ret=%d", sound_format, ret);
        return ret;
    }

    if (!stream->require(1)) {
        ret = ERROR_AAC_DECODE_ERROR;
        srs_error("aac decode aac_packet_type failed. ret=%d", ret);
        return ret;
    }
    
    SrsCodecAudioType aac_packet_type = (SrsCodecAudioType)stream->read_1bytes();
    if (aac_packet_type == SrsCodecAudioTypeSequenceHeader) {
        // AudioSpecificConfig
        // 1.6.2.1 AudioSpecificConfig, in aac-mp4a-format-ISO_IEC_14496-3+2001.pdf, page 33.
        //
        // only need to decode the first 2bytes:
        // audioObjectType, aac_profile, 5bits.
        // samplingFrequencyIndex, aac_sample_rate, 4bits.
        // channelConfiguration, aac_channels, 4bits
        if (!stream->require(2)) {
            ret = ERROR_AAC_DECODE_ERROR;
            srs_error("aac decode sequence header failed. ret=%d", ret);
            return ret;
        }
        
        aac_profile = stream->read_1bytes();
        aac_sample_rate = stream->read_1bytes();
        
        aac_channels = (aac_sample_rate >> 3) & 0x0f;
        aac_sample_rate = ((aac_profile << 1) & 0x0e) | ((aac_sample_rate >> 7) & 0x01);
        aac_profile = (aac_profile >> 3) & 0x1f;
        
        got_sequence_header = true;
        
        return ret;
    }
    
    if (!got_sequence_header) {
        ret = ERROR_AAC_DECODE_ERROR;
        srs_error("aac no sequence header. ret=%d", ret);
        return ret;
    }
    
    // the left is the aac raw frame data.
    int16_t aac_raw_length = stream->size() - stream->pos();
    
    // write the ADTS header.
    // @see aac-mp4a-format-ISO_IEC_14496-3+2001.pdf, page 75,
    //      1.A.2.2 Audio_Data_Transport_Stream frame, ADTS
    // @see https://github.com/winlinvip/simple-rtmp-server/issues/212#issuecomment-64145885
    // byte_alignment()
    
    // adts_fixed_header:
    //      12bits syncword,
    //      16bits left.
    // adts_variable_header:
    //      28bits
    //      12+16+28=56bits
    // adts_error_check:
    //      16bits if protection_absent
    //      56+16=72bits
    // if protection_absent:
    //      require(7bytes)=56bits
    // else
    //      require(9bytes)=72bits
    char aac_fixed_header[7];
    if(true) {
        char* pp = aac_fixed_header;
        int16_t aac_frame_length = aac_raw_length + 7;
        
        // Syncword 12 bslbf
        *pp++ = 0xff;
        // 4bits left.
        // adts_fixed_header(), 1.A.2.2.1 Fixed Header of ADTS
        // ID 1 bslbf
        // Layer 2 uimsbf
        // protection_absent 1 bslbf
        *pp++ = 0xf1;
        
        // Profile_ObjectType 2 uimsbf
        // sampling_frequency_index 4 uimsbf
        // private_bit 1 bslbf
        // channel_configuration 3 uimsbf
        // original/copy 1 bslbf
        // home 1 bslbf
        int8_t fh_Profile_ObjectType = aac_profile - 1;
        *pp++ = ((fh_Profile_ObjectType << 6) & 0xc0) | ((aac_sample_rate << 2) & 0x3c) | ((aac_channels >> 2) & 0x01);
        // @remark, Emphasis is removed, 
        //      @see https://github.com/winlinvip/simple-rtmp-server/issues/212#issuecomment-64154736
        // 4bits left.
        // adts_variable_header(), 1.A.2.2.2 Variable Header of ADTS
        // copyright_identification_bit 1 bslbf
        // copyright_identification_start 1 bslbf
        *pp++ = ((aac_channels << 6) & 0xc0) | ((aac_frame_length >> 11) & 0x03);
        
        // aac_frame_length 13 bslbf: Length of the frame including headers and error_check in bytes.
        // use the left 2bits as the 13 and 12 bit,
        // the aac_frame_length is 13bits, so we move 13-2=11.
        *pp++ = aac_frame_length >> 3;
        // adts_buffer_fullness 11 bslbf
        *pp++ = (aac_frame_length << 5) & 0xe0;
        
        // no_raw_data_blocks_in_frame 2 uimsbf
        *pp++ = 0xfc;
    }
    
    // write 7bytes fixed header.
    if ((ret = _fs->write(aac_fixed_header, 7, NULL)) != ERROR_SUCCESS) {
        return ret;
    }
    
    // write aac frame body.
    if ((ret = _fs->write(data + stream->pos(), aac_raw_length, NULL)) != ERROR_SUCCESS) {
        return ret;
    }
    
    return ret;
}